Dual-chamber, diaphragm type air horn



March 9, 1954 G. D. WOODY DUAL-CHAMBER, DIAPHRAGM TYPE AIR HORN Filed May 31, 1951 INVENTOR. FIG. 2 GEORGE o. WOODY ATTORNEY Patented Mar. 9, 1954 v UNITED STATES PATENT OFFICE DUAL-CHAMBER, DIAPHRAGM TYPE AIR HORN 2 Claims.

My present invention relates to an air horn, and more particularly to a dual-chamber, diaphragm type air horn.

This invention herein disclosed is a modification of the invention disclosed in my co-pending application, Serial No. 207,931, filed January 26, 1951, for Improved Air Horn.

The value of a signal for marine, automotive and other industries cannot be over-emphasized since the safe operation of such industries depends, many times, upon an audible Warning signal. It is therefore highly important in the construction of the signal device that emphasis be placed on the dependability of both operation and intensity of carrying power of the sound produced. Next of importance should be the pitch or tone, the economy of operation, and finally the actual structural design of the mechanism itself. The mechanism should be as foolproof as it is possible to make, for seldom is an air horn blown unless an emergency arises where failure cannot be tolerated.

While considerable efiort was put forth in my (so-pending application to illustrate a horn both pleasing in design and tone quality and to keep the structure compact, certain structural changes have been found desirable. These changes have to deal with the method of getting air more quickly to the rear of the diaphragm as will be hereinafter described in detail.

It has been found that only a certain intensity is available from a given size diaphragm, and also according to the amount of air pressure used. Several of the horns made required air pressure from 60 to 160 lbs. per square inch which necessitates a special compressor, particularly for automotive use. It is apparent, therefore, that a person purchasing and installing such a system would desire a horn of rugged construction and with greatest intensity possible. A further requirement would be some adjustment to the tone quality and to provide the greatest intensity of sound at the least possible amount of initial air pressure.

It is an object of the present invention to provide an improved structure for an air horn which will permit a greater intensity of sound with the same amount of air pressure used without the present invention, such object being accomplished by providing a means of pushing the vibrating diaphragm completely against the trumpet at any pressure, thus causing great sound pressure differentials in the trumpet.

Another object of my invention is to provide means for controlling the amount of differential pressure existing on opposite sides of the diaphragm during a blast, such differential permitting smaller vibrational amplitude in a diaphragm, thus increasing its life.

Another object of the invention is to provide an improved structure for an existing air horn which decreases the volume of used air and at the same time increases the intensity of sound, this object being accomplished by providing a means of pushing the vibrating diaphragm completely against the trumpet at any pressure, thus causing less loss of high pressure air which would normally blow out through the trumpet.

Another object of the invention is to provide passageways for air to go to both sides of the diaphragm at the same time, and to provide a bleed-off valve in order to maintain the desired difierential of pressure on the two sides of the diaphragm.

Another object of my invention is to provide a dual-chamber, diaphragm type air horn in which the back pressure is proportional to the applied pressure.

Still another object of my invention is to provide a dual-chamber diaphragm type of air horn that permits air to enter its back pressure chamber without passing through its diaphragm. A further object of this invention to is provide means causing pressure to be built up against both sides of a horn diaphragm, whereinthe pressures are built up simultaneously to permit the diaphragm to vibrate almost immediately upon the entrance of air into the pressure cham-- ber regardless of the applied pressure from the source.

Further objects and advantages of my invention will become apparent in the course of the following detailed description when viewed together with the accompanying drawing in which:

Fig. l is a cross-sectional view of an air horn embodying the features of my present invention.

Fig. 2 is a rear view of the horn illustrated in Fig. 1.

In the accompanying drawing, the reference character It) indicates the mounting base of a horn such as the Simplex, which is manufactured by the Strombos Company in Michigan. The base It) extends upwardly to form a standard H which supports the air chamber housing l2 and the trumpet 13 in the manner illustrated. The rear face of the housing is prepared to receive the horn diaphragm M which is held rigidly around its peripheral edge by a rear plate 15 in such a manner that the diaphragm is slightly concave in the direction of trumpet l3.

By means of lock nut Hi, the trumpet I3 is positioned through the standard H and the front of the housing [2 and brought to a position just touching the front face of the diaphragm M. The pressure chamber I! is provided with an air inlet hole I8 to receive air from the compressor connection receptacle l8.

In prior art constructions, the back plate l of the horn is provided with a hole (not shown) open to the atmosphere. Thus when air is admitted into the pressure chamber, the pressure must be allowed to build up suiilciently to move the diaphragm l4 away from the end of the trumpet l3 in order for the air to exhaust through the trumpet. As soon as the pressure is relieved, the diaphragm returns to its natural position against the trumpet end until the pressure builds up again. These successive bursts of air produce waves resulting in the sound of the horn. In such constructions, it is readily seen that if the air entering the pressure chamber I! is not the exact desired pressure or is too high, the pressure will force the diaphragm M rearwardly and hold the same in this position until the pressure decreases to such an amount that the diaphragm M will begin to vibrate. This defect found in horns of the prior art is the cause of the initial swishing sound of air coming from the horn just prior to hearing the sound when high pressure air is applied. It is of course understood that the use of reference characters i4 and I! in the above statement is strictly for reference sake, since this defect in air horns is overcome by the present invention.

Should the applied air pressure be extremely high, the diaphragm of the prior art horns will be held completely away from the trumpet and there will be no sound at all, other than the rush of the escaping air. It is apparent, therefore, that the intensity of sound from a given size diaphragm bears a definite relationship to the amount of air pressure used to actuate it, and this intensity is not in proportion to applied pressure but rather depends on a critical pressure which is determined by the diaphragm strength.

In my improvements to the presently constructed horn, I have overcome the above-mentioned defects very inexpensively by providing a passageway 19 from compressor connection receptacle [8' to the back pressure chamber 29 defined by the rear of the diaphragm Hi and the back plate I5. I have furthermore provided a fitting 2| constituting a controlled exhaust for the back pressure chamber 20,. the fitting containing an adjustable needle valve 22. Thus, when air is admitted into the pressure chamber II it is also admitted to the back pressure chamber 20, so that when the diaphragm I4 is moved rearwardly, it is pushed against a cushion created. by the back pressure existing in the back pressure chamber 20. By adjusting the needle valve 22, any amount of actual back pressure may be created. It is understood also, that if the exhaust from the back pressure chamber were cut oiT altogether by closing the valve 22, the pressures on each side of the diaphragm would soon equalize, and the horn would fail to sound. The diameter'of the passageway l9 bears such relationship to the choke, or air inlet l8 to the pressure chamber I7, that an even diiTerentia-l of pressure can be maintained, such differential being further adjustable by means of the. needle valve 22.

With the diaphragm being pushed rearwardly by the high pressure air against a. slight cushion or back pressure, it will naturally return to its plane of rest against the trumpet end more completely and in a shorter length of time thus permitting less vibrational amplitude and greater intensity of sound. By actual experimentation it has been found that the above improvement applied to an existing horn has substantially doubled its intensity of sound. Moreover, because the back pressure behind my diaphragm is proportional to the applied pressure, the effective diaphragm strength will decrease as the air pressure in small storage tanks decreases during a blast so that the horn will blow continuously with a maximum of efificiency at any pressure. Such construction further adds to the life of the diaphragm since it reduces the actual amplitude which causes strain and fatigue of the material of which it is made.

Moreover, this invention permits the diaphragm to vibrate immediately upon entrance of air to the pressure chamber and actually uses less air in its operation due to the diaphragm movement described above.

While being of great value to existing air horns, this invention adds but very little to their manufacturin cost and of course it does not detract from the overall appearance of the horn as presently being marketed. This device may be made to conform to the operation of various air horns whether for marine or automotive cars or in fact in any other industry where air horns are used.

It is understood of course that this invention is subject to certain changes and modifications by those experienced in the art, and such changes and modifications are to be considered as coming within the scope of the specification and the following claims.

I claim:

1. In a iiuid operated horn having a diaphragm releasably pressed against a fluid outlet, a pressure chamber on the side of said diaphragm adiacent said outlet, a back pressure chamber on the other side of said diaphragm, means for admitting fluid under pressure substantially simultaneously to both said pressure chamber and said back pressure chamber, and vent means for venting fluid from said back pressure chamber, said vent means comprising a restricted opening controllin a flow of less capacity than said means for admitting fluid under pressure to both said pressure chamber and said back pressure chambar.

2. In a fluid operated hornhaving a diaphragm releasably pressed against a fluid outlet, a pressure chamber on the side of'said diaphragm adjacent said outlet, a back pressure chamber 011 the other side of said diaphragm, means for admitting fluid under pressure substantially simultaneously to both said pressure chamber andsaid back pressure chamber, and adjustable vent means for selectively controlling the venting of fluid from said back pressure chamber, said vent means comprising a restricted opening controlling a flow of less capacity than said means for admitting fluid under pressure to both said pressure chamber and said back pressure chamber.

GEORGE D. WOODY.

References Gited in the file of this patent UNITED STATES PATENTS Number Name Date 1,281,877 Teste-et al. Oct. 15,1918 1,805,627 Kelley May 19,. 1931 2,177 594 Eaves Qct. 24,.1939 2,273,968 Lewis Feb.- 24, 1-942 

